Wash the idli rice and fenugreek seeds separately. Soak them overnight or for at least 8–10 hours.
Drain the soaked fenugreek seeds and grind them smoothly by adding water little by little. The batter should become light and foamy. When dropped into water, the batter should slightly float.
Now grind the soaked idli rice into a smooth butter-like batter texture.
Transfer the rice batter to the same bowl as the fenugreek batter. Mix both well together. Add little water if needed to bring it to dosa batter consistency.
Dissolve powdered karuppatti in 1.5 cups water and keep the syrup ready.
Heat a heavy-bottom pan and add 3/4 cup water with little salt. Slowly pour the prepared batter into the pan while stirring continuously on low flame.
Cook for about 15 minutes until the batter thickens and the raw smell disappears.
Switch off the flame and slowly add the prepared karuppatti syrup. Mix continuously using a whisk or spatula until combined smoothly.
Turn on the flame again and continue cooking on low flame. Stir continuously for around 20 minutes.
Add sesame oil little by little in between as the kali thickens.
The vendhaya kali is ready when it becomes glossy and non-sticky.
To check the consistency, wet your hands with cold water and roll a small portion into a ball. If it rolls without sticking, the kali is perfectly cooked.
Serve hot or warm with extra sesame oil if preferred.